Patent GB-1117875-A (GB)
Title: Coating composition
IPC: C25D13/00
Filed: 1966-04-25
Abstract: An electrodepositable coating composition is obtained by ageing a composition comprising a polycarboxylic resinous vehicle, strontium chromate, and water at a pH below 7.0 to reduce the level of soluble chromate ions to below 300 p.p.m.  The vehicle may be an alkyd resin or mixture thereof with an aminoplast. Example V discloses a resin derived from pentaerythritol, linseed oil, trimethylolethane, phthalic anhydride, and dimethylolpropionic acid.  The resin may be solubilized by reaction with an amine or ammonia.  Conventional pigments, anti-oxidants, wetting-agents and driers are included, and de-ionized water is preferred in making up.  The aqueous composition may contain 1-20% by weight non-volatile solids before ageing and 30-99% after ageing and concentrating.ALSO:An electrodepositable coating composition is obtained by aging a composition comprising a polycarboxylic resinous vehicle, strontium chromate, and water at a pH below 7.0 to reduce the level of soluble chromate ions to below 300 p.p.m.  The polycarboxylic resinous vehicle may be (i) the reaction product of a drying oil fatty acid ester and an a ,b -ethylenically unsaturated carboxylic acid or anhydride thereof and, optionally, another ethylenically unsaturated monomer; or (ii) an at least partially neutralized interpolymer of at least one hydroxyalkyl ester of an unsaturated carboxylic acid, at least one unsaturated carboxylic acid and at least one other ethylenically unsaturated monomer optionally together with an amine-aldehyde condensation product and/or a polyepoxide; or (iii) an alkyd resin plus an amine-aldehyde resin, and it may be solubilized by reaction wih an amine or ammonia.  Conventional pigments e.g. iron oxide, hydrated iron oxide, lead oxide, titanium dioxide, carbon black, talc, barium sulphate, cadmium yellow or red, chromic yellow, phthalocyanine blue or toluidine red may be included, and the composition may contain o-amyl phenol or cresol as anti-oxidant, and conventional wetting-agents and driers.  The aqueous composition before aging may contain 1-20% by weight non-volatile solids and after aging and concentrating 30-99%; de-ionised water is preferred.  Examples I-IV disclose compositions based on the solubilized reaction product of 4 parts by weight linseed oil and 1 maleic anhydride.ALSO:An aqueous electro-coating bath used for coating a cathode or anode, particularly the anode, is obtained by ageing a composition comprising a polycarboxylic resinous vehicle, strontium chromate, and water at a pH below 7.0 for a time sufficient to reduce the soluble chromate ions to below 300 p.p.m.  Suitable electro-coating conditions are 1 to several thousand volts, typically 50-500 volts, and a current density of 0.1-15 amps per square foot. The coating may be baked.  The polycarboxylic resinous vehicle may be (i) the reaction product of a drying oil fatty acid ester and an a , b -ethylenically unsaturated carboxylic acid or anhydride thereof and, optionally, another ethylenically unsaturated monomer, or (ii) an at least partially neutralized interpolymer of at least one hydroxyalkyl ester of an unsaturated carboxylic acid, at least one unsaturated carboxylic acid and at least one other ethylenically unsaturated monomer optionally together with an amine-aldehyde condensation product and/or a polyepoxide or (iii), an alkyd resin plus an amine-aldehyde resin, and it may be solubilized by reaction with an amine or ammonia.  Conventional pigments e.g. iron oxide, hydrated non-oxide, lead oxide, titanium dioxide, carbon black, talc, barium sulphate, cadmium yellow or red, chromic yellow, phthalocyanine blue or tolidine red may be included and the composition may contain o-amyl phenol or cresol as anti-oxidant, and conventional wetting-agents and driers.  The aqueous composition before ageing may containALSO:An aqueous electro-coating bath used for coating a cathode or anode, particularly the anode, is obtained by ageing a composition comprising a polycarboxylic resinous vehicle, strontium chromate, and water at a pH below 7.0 for a time sufficient to reduce the soluble chromate ions to below 300 p.p.m.  Suitable electro-coating conditions are 1 to several thousand volts, typically 50-500 volts, and a current density of 0.1 - 15 amps per square foot. The coating may be baked.  The polycarboxylic resinous vehicle may be (i) the reaction product of a drying oil fatty acid ester and an a , b -ethylenically unsaturated carboxylic acid or anhydride thereof and, optionally, another ethylenically unsaturated monomer, or (ii) an at least partially neutralized interpolymer of at least one hydroxyalkyl ester of an unsaturated carboxylic acid, at least one unsaturated carboxylic acid and at least one other ethylenically unsaturated monomer optionally together with an amine-aldehyde condensation product and/or a polyepoxide or (iii), an alkyd resin plus an amine-aldehyde resin, and it may be solubilized by reaction with an amine or ammonia.  Conventional pigments e.g. iron oxide, hydrated non-oxide, lead oxide, titanium dioxide, carbon black, talc, barium sulphate, cadmium yellow or red, chromic yellow, phthalocyanine blue or tolidine red may be included and the composition may contain o-amyl phenol or cresol as anti-oxidant, and conventional wetting-agents and driers.  The aqueous composition before ageing may contain <FORM:1117875/C6-C7/1> wherein M is Sb, As, Bi, Fe, Se or Te, X may be present or absent and if present represents a dialkycysteinyl group of the formula CH(COOH)(NH2).C(CH3)2.S-or CH(COOH)(NH2).C(CH3)(C2H5).S-Y is dimethylcysteine or methylethylcysteine, Z is X, -Sb.X2 or a carbon linked substituted or unsubstituted alkyl, aryl or aralkyl group, or the remainder of an organic residue comprising a heterocyclic ring in which M is included. k is 0, 1 or 2, n is an integer consistent with the valencies of M and Z, and each Z may represent the same or different radicals if n is greater than 1, and m is an integer such that the total number of dialkylcysteinyl groups and complex forming dialkylcysteine molecules present does not exceed the maximum number of co-ordinate bonds which can be formed by the metal, or, if X is present, m may be 0, are prepared by electrolysis of an inorganic salt of the desired metal dissolved in a solution containing water and the dialkylcysteine. In an example ferrous sulphate and dimethylcysteine in solution in aqueous glycerol was electrolyzed at 0.5 mA and 200 volts in a U-tube and the solution from the cathodic side was collected and a mixture of ferrous and ferric dimethylcysteine isolated by precipitation with diethyl ether and ethanol.  (It is stated that by maintaining a tight hydrogen chamber on the cathodic side of the tube oxidation of the ferrous form is avoided.)